Xanthocyparis
| Xanthocyparis | ||||||||||||
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Nootka cypress ( Xanthocyparis nootkatensis ) |
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| Scientific name | ||||||||||||
| Xanthocyparis | ||||||||||||
| Farjon & Hiep |
Xanthocyparis is a plant genus in the family of the cypress family (Cupressaceae). The genus Xanthocyparis has a strongly disjoint area with only one species in North America and one in northern Vietnam .
Vegetative characteristics
Xanthocyparis species grow as small to large, evergreen trees . The bark is fibrous and flakes off in longitudinal strips. The heartwood is yellowish and grows slowly. They form a pyramidal, conical or an irregular crown that is flat on top. The seedlings have two seed leaves ( cotyledons ), the result leaves are linealische juvenile needle leaves in four whorls .
The leafy branches are horizontal or hanging slightly. There are three types of foliage: linear-needle-shaped juvenile leaves, transitional leaves and scale-shaped adult leaves. Juvenile leaves are either only present on the seedlings or also on adult trees. They stand in whorls of four and stand out radially from the axis. Branches with these foliage are sterile. Transitional leaves are also only found on seedlings or even on adult trees. Adult leaves are only found on adult trees. They are cross-opposed and have two sizes and shapes: the lateral ones are strongly flattened. Twigs with adult leaves are often fertile and have cones .
Generative characteristics
Xanthocyparis species are single sexed ( monoecious ). The pollen-forming cones are terminal and individually on small branches with scale leaves. The pollen-forming cones are 2.5 to 5 × 2 to 2.5 millimeters in size and carry 10 to 16 microsporophylls . The microsporophylls are opposite, shield-shaped and carry two (rarely three) large microsporangia .
The seed-bearing cones are terminally and individually on side branches with scale leaves. Mature cones are 7 to 11 × 10 to 12 millimeters in size when they open even wider. The bract-scale complexes are in two (rarely three) opposite pairs. They are fused at the base. The upper pair is completely fused and opens wide to release the seeds. They are flap to slightly shield-shaped, and have a central umbo. The central axis of the pin is small and can also be completely absent. The ovules are axillary in the bracts, each bract has one to five ovules, from which usually fewer seeds arise. Usually seeds develop only on the upper pair of bracts and scales. The seeds are flattened and have two lateral wings.
Systematics and distribution
The genus Xanthocyparis was only established in 2002. The generic name Xanthocyparis means "yellow cypress" and refers to the color of the wood.
The genus Xanthocyparis is placed in the subfamily Cupressoideae , its closest relatives are Cupressus and Juniperus .
The genus Xanthocyparis has a strongly disjoint area . One of the two species is found in North America, the second in northern Vietnam.
There are two species belonging to the genus Xanthocyparis :
- Nootka false cypress ( Xanthocyparis nootkatensis (D.Don) Farjon & DKHarder ) from North America was previously included in the genus Chamaecyparis and was transferred to the new genus in 2002 after the discovery of the Vietnamese species.
- Xanthocyparis vietnamensis Farjon & THNguyên : The discovery of this Vietnamese species in 1999 led to the establishment of the new genus in 2002.
The close relationship between the two species was beyond dispute. However, Little and colleagues found out in 2004 that the Nootka false cypress had been described by Oersted in 1865 under the generic name Callitropsis . But the name was never used. They transferred the two species to the genus Callitropsis Oerst. Against this was raised in 2006 by Miller and Farjon; they suggested, however, the preservation of the name Xanthocyparis against the older Callitropsis . This proposal was endorsed by the Nomenclature Committee for Vascular Plants in 2007. A decision on the acceptance of Xanthocyparis as a noun conservandum will be made in 2011 at the next International Botanical Congress. The name Xanthocyparis was preserved with the type species Xanthocyparis vietnamensis .
Some authors assign both species to the genus Cupressus L. as Cupressus nootkatensis D. Don ex Lambert and Cupressus vietnamensis (Farjon et THNguyèn) Silba .
supporting documents
literature
- A. Farjon, Nguyen Tien Hiep, DK Harder, Phan Ke Loc, L. Averyanov: A New Genus and Species in Cupressaceae (Coniferales) from Northern Vietnam, Xanthocyparis vietnamensis. In: Novon , Volume 12, 2002, pp. 179-189.
Individual evidence
- ↑ a b c d e A. Farjon, Nguyen Tien Hiep, DK Harder, Phan Ke Loc, L. Averyanov: A New Genus and Species in Cupressaceae (Coniferales) from Northern Vietnam, Xanthocyparis vietnamensis. In: Novon , Volume 12, 2002, pp. 179-189.
- ^ A b Damon P. Little, Andrea E. Schwarzbach, Robert P. Adams, Chang-Fu Hsieh: The circumscription and phylogenetic relationships of Callitropsis and the newly described genus Xanthocyparis (Cupressaceae). In: American Journal of Botany , Volume 91, 2004, pp. 1872-1881. on-line.
- ^ Robert R. Mill, Aljos Farjon: Proposal to conserve the name Xanthocyparis against Callitropsis Oerst. (Cupressaceae). In: Taxon , Volume 55, 2006, pp. 229-231.
- ^ RK Brummitt: Report of the Nomenclature Committee for Vascular Plants: 59. In: Taxon , Volume 56, 2007, pp. 1289-1296. Here p. 1290f.
- ↑ Rafaël Govaerts (ed.): Xanthocyparis. In: World Checklist of Selected Plant Families (WCSP) - The Board of Trustees of the Royal Botanic Gardens, Kew . Retrieved March 22, 2019.
- ^ Xanthocyparis in the Germplasm Resources Information Network (GRIN), USDA , ARS , National Genetic Resources Program. National Germplasm Resources Laboratory, Beltsville, Maryland. Retrieved March 22, 2019.
- ↑ Christopher J. Earle, 2019: Cupressus at The Gymnosperm Database .
- ↑ Kangshan Mao, Hao Gang, Liu Jianquan, RP Adams, RI Milne: Diversification and biogeography of Juniperus (Cupressaceae): variable diversification rates and multiple intercontinental dispersals. In: New Phytologist , Volume 188, Issue 1, 2010, pp. 254-272.
